How to get all collections of the current scene?
Recursively walk the tree.

Similarly to https://blender.stackexchange.com/a/137866/15543 and Sorting Collections Alphabetically in the Outliner

import bpy

def traverse_tree(t):
    yield t
    for child in t.children:
        yield from traverse_tree(child)

coll = bpy.context.scene.collection

for c in traverse_tree(coll):
    print(c.name)